Composition containing dopant and co-polymers having non-conjugated spacer units and its use in OLED devices

ABSTRACT

A polymer comprising repeat units of formula (I) and one or more co-repeat units: 
     
       
         
         
             
             
         
       
         
         Ar 1  in each occurrence independently represent an aryl or heteroaryl group; 
         R 1  and R 2  in each occurrence independently represent a substituent; 
         p independently in each occurrence is 0 or a positive integer; 
         Sp represents a spacer group comprising at least one carbon or silicon atom spacing the two groups Ar 1  apart; and 
         each group Ar 1  is bound to an aromatic group of a co-repeat unit. 
       
    
     The polymer may form a charge-transporting layer of an OLED or may be a host material used with a luminescent dopant in a light-emitting layer of an OLED.

RELATED APPLICATIONS

This application claims Foreign priority benefits under 35 U.S.C.§119(a)-(d) or 35 U.S.C. §365(b) of British application number1221624.8, filed Nov. 30, 2012, the entirety of which is incorporatedherein.

BACKGROUND OF THE INVENTION

Electronic devices containing active organic materials are attractingincreasing attention for use in devices such as organic light emittingdiodes (OLEDs), organic photoresponsive devices (in particular organicphotovoltaic devices and organic photosensors), organic transistors andmemory array devices. Devices containing active organic materials offerbenefits such as low weight, low power consumption and flexibility.Moreover, use of soluble organic materials allows use of solutionprocessing in device manufacture, for example inkjet printing orspin-coating.

An OLED may comprise a substrate carrying an anode, a cathode and one ormore organic light-emitting layers between the anode and cathode.

Holes are injected into the device through the anode and electrons areinjected through the cathode during operation of the device. Holes inthe highest occupied molecular orbital (HOMO) and electrons in thelowest unoccupied molecular orbital (LUMO) of a light-emitting materialcombine to form an exciton that releases its energy as light.

A light emitting layer may comprise a semiconducting host material and alight-emitting dopant wherein energy is transferred from the hostmaterial to the light-emitting dopant. For example, J. Appl. Phys. 65,3610, 1989 discloses a host material doped with a fluorescentlight-emitting dopant (that is, a light-emitting material in which lightis emitted via decay of a singlet exciton).

Phosphorescent dopants are also known (that is, a light-emitting dopantin which light is emitted via decay of a triplet exciton).

A hole-transporting layer may be provided between the anode andlight-emitting layer of an OLED.

Suitable light-emitting materials include small molecule, polymeric anddendrimeric materials. Suitable light-emitting polymers includepoly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polymerscontaining arylene repeat units, such as fluorene repeat units. Bluelight-emitting fluorene homopolymer is disclosed in WO 97/05184.

WO 00/53656 discloses a method of forming a conjugated polymer byreacting a monomer carrying halide reactive functional groups and amonomer carrying boron derivative reactive functional groups in thepresence of a palladium catalyst.

WO 2005/013386 discloses an organic light-emitting device comprising ahost polymer material and a luminescent metal complex wherein thepolymer material may comprise non-planar repeat units or partially orfully non-conjugated repeat units in order to reduce conjugation of thepolymer.

WO 2011/141709 discloses a light-emitting composition comprising a hostpolymer and a light-emitting dopant wherein the host polymer comprisesconjugating repeat units and non-conjugating repeat units in a backboneof the polymer. The non-conjugating repeat units comprise an at leastpartially saturated ring having at least one ring atom that breaks anyconjugation path between repeat units linked to the non-conjugatingrepeat units.

WO 2010/085676 discloses host materials for electrophosphorescentdevices. A copolymer formed by copolymerization of1,6-bis(3-(4,4,5,5-tetramethyl-[1,3,2]-dioxaborolan-2-yl)phenoxyl)hexaneand2-(4-(3-(3,6-dibromocarbazol-9-yl)propyl)phenyl)-4,6-di(3-methylphenyl)-1,3,5-triazineis disclosed.

JP 2005/158561 discloses non-conjugated polymers containing an electrontransporting compound.

US 2011/095269 discloses the following polymer:

WO 2012/048778 discloses polymers formed by polymerization of thefollowing monomers:

U.S. Pat. No. 7,898,163 discloses a monomer having the followingformula:

SUMMARY OF THE INVENTION

In a first aspect the invention provides a polymer comprising repeatunits of formula (I) and one or more co-repeat units:

wherein Ar¹ in each occurrence independently represents an aryl orheteroaryl group;

R¹ and R² in each occurrence independently represent a substituent;

p independently in each occurrence is 0 or a positive integer;

Sp represents a spacer group comprising at least one carbon or siliconatom spacing the two groups Ar¹ apart; and

each group Ar¹ is bound to an aromatic group of a co-repeat unit.

In a second aspect the invention provides a monomer of formula (Im):

wherein LG is a leaving group capable of leaving in a coupling reactionto form a carbon-carbon bond between Ar¹ and an aromatic orheteroaromatic group, and Ar¹, R¹, R², p and Sp are as described in thefirst aspect.

In a third aspect the invention provides a method of forming a polymeraccording to the first aspect, the method comprising the step ofpolymerising a monomer according to the second aspect and one or moreco-monomers for forming the one or more respective co-repeat units.

In a fourth aspect the invention provides a composition comprising apolymer according to the first aspect and at least one light-emittingdopant.

In a fifth aspect the invention provides a formulation comprising apolymer according to the first aspect or a composition according to thefourth aspect and at least one solvent.

In a sixth aspect the invention provides an organic light-emittingdevice comprising an anode, a cathode and one or more organic layersbetween the anode and cathode including a light-emitting layer whereinat least one of the one or more organic layers comprises a polymeraccording to the first aspect.

In a seventh aspect the invention provides a method of forming anorganic light-emitting device according to the sixth aspect, the methodcomprising the step of forming the light-emitting layer over one of theanode and the cathode and forming the other of the anode and the cathodeover the light-emitting layer

DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to thedrawings in which:

FIG. 1 illustrates an OLED according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an OLED 100 according to an embodiment of theinvention comprising an anode 101, a cathode 105 and a light-emittinglayer 103 between the anode and cathode. The device 100 is supported ona substrate 107, for example a glass or plastic substrate.

One or more further layers may be provided between the anode 101 andcathode 105, for example hole-transporting layers, electron transportinglayers, hole blocking layers and electron blocking layers. The devicemay contain more than one light-emitting layer.

Preferred device structures include:

Anode/Hole-injection layer/Light-emitting layer/Cathode

Anode/Hole transporting layer/Light-emitting layer/Cathode

Anode/Hole-injection layer/Hole-transporting layer/Light-emittinglayer/Cathode

Anode/Hole-injection layer/Hole-transporting layer/Light-emittinglayer/Electron-transporting layer/Cathode.

Preferably, at least one of a hole-transporting layer and hole injectionlayer is present. Preferably, both a hole injection layer andhole-transporting layer are present.

Light-emitting materials include red, green and blue light-emittingmaterials.

A blue emitting material may have a photoluminescent spectrum with apeak in the range of 400-490 nm, optionally 420-490 nm.

A green emitting material may have a photoluminescent spectrum with apeak in the range of more than 490 nm up to 580 nm, optionally more than490 nm up to 540 nm.

A red emitting material may optionally have a peak in itsphotoluminescent spectrum of more than 580 nm up to 630 nm, optionally585-625 nm.

Light-emitting layer 103 may contain a polymer of the invention. Thepolymer may be doped with one or more luminescent dopants. Thelight-emitting layer 103 may consist essentially of the polymer and theone or more luminescent dopants, or may contain one or more furthermaterials, for example one or more charge-transporting materials or oneor more further light-emitting materials. When used as a host materialfor one or more light-emitting dopants, the singlet or triplet energylevel of the host material is preferably no more than 0.1 eV below thatof the light-emitting material, and is more preferably about the same orhigher than that of the light-emitting material in order to avoidquenching of luminescence from the light-emitting dopant.

In a preferred embodiment, light-emitting layer 103 contains a polymerof the invention and at least one of green and blue phosphorescentlight-emitting materials.

A charge-transporting layer adjacent to a phosphorescent light-emittinglayer preferably contains a charge-transporting material having a T₁excited state energy level that is no more than 0.1 eV lower than,preferably the same as or higher than, the T₁ excited state energy levelof the phosphorescent light-emitting material(s) of the invention inorder to avoid quenching of triplet excitons migrating from thelight-emitting layer into the charge-transporting layer. Accordingly, apolymer of the invention may be used as a charge-transporting materialin a charge-transporting layer. In one preferred arrangement, ahole-transporting layer comprises or consists essentially of thepolymer.

Triplet energy levels may be measured from the energy onset of thephosphorescence spectrum measured by low temperature phosphorescencespectroscopy (Y. V. Romaovskii et al, Physical Review Letters, 2000, 85(5), p 1027, A. van Dijken et al, Journal of the American ChemicalSociety, 2004, 126, p 7718).

The polymer contains non-conjugating repeat units of formula (I)

The repeat units of formula (I) contain aromatic or heteroaromaticgroups Ar¹ spaced apart by a spacer group Sp. The spacer group does notprovide any conjugation path between the two groups Ar¹, and thereforedoes not provide any conjugation path between repeat units on eitherside of the non-conjugating repeat units of formula (I).

However the groups Ar¹ are capable of conjugating to aromatic orheteroaromatic groups of repeat units adjacent to the repeat unit offormula (I). The present inventors have found that even this relativelylimited extent of conjugation between the repeat unit of formula (I) andan adjacent repeat unit can result in poor device performance,particularly when the polymer is used as a host for a dopant with a highexcited state energy level, such as a phosphorescent green or bluelight-emitting material.

Without wishing to be bound by any theory, it is believed that this poordevice performance may be due to a reduction in singlet and tripletexcited state energy levels upon conjugation. By providing substituentsR¹ on the groups Ar¹ adjacent to the positions through which the repeatunits of formula (I) are linked to adjacent repeat units, sterichindrance may be created between the groups Ar¹ and the aromatic groupsbound of adjacent repeat units that are bound to Ar¹, creating a twistbetween repeat units of formula (I) and adjacent repeat units andreducing the extent of conjugation therebetween. The relatively hightriplet excited state energy level may make the polymers of theinvention suitable for use as hosts for phosphorescent light-emittingmaterials, including red, green and blue phosphorescent light-emittingmaterials, and/or as charge-transporting materials adjacent tolight-emitting layers containing phosphorescent light-emitting materials

The polystyrene-equivalent number-average molecular weight (Mn) measuredby gel permeation chromatography of the polymers described herein may bein the range of about 1×10³ to 1×10⁸, and preferably 1×10⁴ to 5×10⁶. Thepolystyrene-equivalent weight-average molecular weight (Mw) of thepolymers described herein may be 1×10³ to 1×10⁸, and preferably 1×10⁴ to1×10⁷.

Polymers as described herein are suitably amorphous polymers.

Polymer Synthesis

Polymers as described herein may be formed by a polymerisation carriedout in the presence of a metal catalyst.

One method of forming conjugated or partially conjugated polymers isSuzuki polymerisation, for example as described in WO 00/53656 or U.S.Pat. No. 5,777,070 which allows formation of C—C bonds between twoaromatic or heteroaromatic groups, and so enables formation of polymershaving conjugation extending across two or more repeat units. Suzukipolymerisation takes place in the presence of a palladium complexcatalyst and a base.

As illustrated in Scheme 1, in the Suzuki polymerisation process amonomer for forming repeat units RU1 having leaving groups LG1 such asboronic acid or boronic ester groups undergoes polymerisation with amonomer for forming repeat units RU2 having leaving groups LG2 such ashalogen, preferably bromine or iodine; sulfonic acid; or sulfonic esterto form a carbon-carbon bond between Arylene 1 and Arylene 2:nLG1-RU1-LG1+nLG2-RU2-LG2→-(RU1-RU2)_(n)-  Scheme 1

Exemplary boronic esters have formula (IV):

-   -   (IV)

wherein R⁶ in each occurrence is independently a C₁₋₂₀ alkyl group, *represents the point of attachment of the boronic ester to an aromaticring of the monomer, and the two groups R⁶ may be linked to form a ring.In a preferred embodiment, the two groups R⁶ are linked to form thepinacol ester of boronic acid:

It will be understood by the skilled person that a monomer LG1-RU1-LG1will not polymerise to form a direct carbon-carbon bond with anothermonomer LG1-RU1-LG1. A monomer LG2-RU2-LG2 will not polymerise to form adirect carbon-carbon bond with another monomer LG2-RU2-LG2.

Preferably, one of LG1 and LG2 is bromine or iodine and the other is aboronic acid or boronic ester.

This selectivity means that the ordering of repeat units in the polymerbackbone can be controlled such that all or substantially all RU1 repeatunits formed by polymerisation of LG1-RU1-LG1 are adjacent, on bothsides, to RU2 repeat units.

In the example of Scheme 1 above, an AB copolymer is formed bycopolymerisation of two monomers in a 1:1 ratio, however it will beappreciated that more than two or more than two monomers may be used inthe polymerisation, and any ratio of monomers may be used.

The base may be an organic or inorganic base. Exemplary organic basesinclude tetra-alkylammonium hydroxides, carbonates and bicarbonates.Exemplary inorganic bases include metal (for example alkali or alkaliearth) hydroxides, carbonates and bicarbonates.

The palladium complex catalyst may be a palladium (0) or palladium (II)compound.

Particularly preferred catalysts aretetrakis(triphenylphosphine)palladium (0) and palladium (II) acetatemixed with a phosphine.

A phosphine may be provided, either as a ligand of the palladiumcompound catalyst or as a separate compound added to the polymerisationmixture. Exemplary phosphines include triarylphosphines, for exampletriphenylphosphines wherein each phenyl may independently beunsubstituted or substituted with one or more substituents, for exampleone or more C₁₋₅ alkyl or C₁₋₅ alkoxy groups.

Particularly preferred are triphenylphospine andtris(ortho-methoxytriphenyl) phospine.

The polymerisation reaction may take place in a single organic liquidphase in which all components of the reaction mixture are soluble. Thereaction may take place in a two-phase aqueous-organic system, in whichcase a phase transfer agent may be used. The reaction may take place inan emulsion formed by mixing a two-phase aqueous-organic system with anemulsifier.

The polymer may be end-capped by addition of an end-capping reactant.Suitable end-capping reactants are aromatic or heteroaromatic materialssubstituted with only one leaving group. The end-capping reactants mayinclude reactants substituted with a halogen for reaction with a boronicacid or boronic ester group at a polymer chain end, and reactantssubstituted with a boronic acid or boronic ester for reaction with ahalogen at a polymer chain end. Exemplary end-capping reactants arehalobenzenes, for example bromobenzene, and phenylboronic acid.End-capping reactants may be added during or at the end of thepolymerisation reaction.

Non-Conjugating Repeat Units

Ar¹ of formula (I) is preferably an aryl group, more preferablyphenylene. Phenylene groups Ar¹ may be 1,2-, 1,3- or 1,4-linkedphenylene, preferably 1,4-linked phenylene.

Exemplary groups R¹ and (where present) R² include C₁₋₄₀ hydrocarbyl,—OR¹¹, —SR¹¹, —NR¹¹ ₂, and —SiR¹¹ ₃ wherein R¹¹ in each occurrence is asubstituent, preferably C₁₋₄₀ hydrocarbyl.

Optionally, R¹ is a C₁₋₄₀ hydrocarbyl, which may the same or differentin each occurrence.

Exemplary hydrocarbyl groups R¹, R² and R¹¹ include C₁₋₂₀ alkyl;unsubstituted phenyl; phenyl substituted with one or more C₁₋₂₀ alkylgroups; and a branched or linear chain of phenyl groups wherein eachphenyl is unsubstituted or substituted with one or more C₁₋₂₀ alkylgroups. C₁₋₂₀ alkyl is preferred.

One or more non-adjacent C atoms of R¹ and, where present, R² mayindependently be replaced with —O—, —S—, —NR₁₁—, —SiR₁₁ ²—, C(═O) or—COO—.

Alkyl groups as described anywhere herein includes linear, branched andcyclic alkyl groups. In the case of R¹, a C₃₋₂₀ branched alkyl group,including alkyl groups containing one or more C atoms selected fromsecondary and tertiary carbon atoms, may provide more steric hindranceand therefore a greater degree of twisting than a corresponding linearalkyl group.

Sp of formula (I) is optionally a C₁₋₂₀ alkyl group wherein one or morenon-adjacent C atoms of the alkyl group may be replaced with O, S,—NR₁₁—, —SiR₁₁ ²—, —C(═O)— or —COO— and wherein R¹¹ in each occurrenceis independently H or a substituent.

Sp of formula (I) may contain a single non-conjugating atom only betweenthe two groups Ar¹, or Sp may contain non-conjugating chain of at least2 atoms separating the two groups Ar¹.

A non-conjugating atom may be, for example, —CR⁴ ₂— or —SiR⁴ ₂— whereinR⁴ in each occurrence is H or a substituent, optionally a substituentR¹¹ as described above, for example C₁₋₂₀ alkyl.

A spacer chain Sp may contain two or more atoms separating the twogroups Ar¹, for example a C₁₋₂₀ alkyl chain wherein one or morenon-adjacent C atoms of the chain may be replaced with O, S, —NR₁₁—,—SiR₁₁ ²—, —C(═O)— or —COO—. Preferably, the spacer chain Sp contains atleast one sp³-hybridised carbon atom separating the two groups Ar¹.

Preferred groups Sp are selected from C₁₋₂₀ alkyl wherein one or morenon-adjacent C atoms are replaced with O. An oligo-ether chain, forexample a chain of formula —O(CH₂CH₂O)_(n)— may be provided, wherein nis from 1-5.

Repeat units of formula (I) may be provided in an amount in the range of1-50 mol %, optionally 20-50 mol %. The polymer may contain two or moredifferent repeat units of formula (I).

The repeat unit of formula (I) may have formula (Ia) or (Ib):

Exemplary repeat units of formula (I) include the following:

wherein R¹¹ in each occurrence is independently H or a substituent.

Co-Repeat Units

Polymers of the invention contain repeat units of formula (I) and one ormore co-repeat units. Some or all of the co-repeat units contain anaromatic or heteroaromatic group that is bound to Ar¹ of repeat units offormula (I).

Exemplary co-repeat units include arylene or heteroarylene repeat unitsthat may be unsubstituted or substituted with one or more substituents,and charge-transporting repeat units containing aromatic orheteroaromatic groups.

Co-repeat units include repeat units that may be directly adjacent torepeat units of formula (I) and repeat units that may be spaced apartfrom repeat units of formula (I). The copolymer may contain repeat unitsof formula (I) and adjacent co-repeat units only in the form of aregioregular AB copolymer of repeat units of formula (I) and adjacentco-repeat units, or it may contain repeat units of formula (I),co-repeat units adjacent to repeat units of formula (I), and one or morefurther co-repeat units

Exemplary co-repeat units include arylene repeat units, for example1,2-, 1,3- and 1,4-phenylene repeat units, 3,6- and 2,7-linked fluorenerepeat units, indenofluorene, naphthalene, anthracene and phenanthrenerepeat units, and stilbene repeat units, each of which may beunsubstituted or substituted with one or more substitutents, for exampleone or more C₁₋₃₀ hydrocarbyl substituents.

One preferred class of arylene repeat units is phenylene repeat units,such as phenylene repeat units of formula (III):

wherein q in each occurrence is independently 0, 1, 2, 3 or 4,optionally 1 or 2; n is 1, 2 or 3; and R³ independently in eachoccurrence is a substituent.

Where present, each R³ may independently be selected from the groupconsisting of:

-   -   alkyl, optionally C₁₋₂₀ alkyl, wherein one or more non-adjacent        C atoms may be replaced with optionally substituted aryl or        heteroaryl, O, S, substituted N, C═O or —COO—, and one or more H        atoms may be replaced with F;    -   aryl and heteroaryl groups that may be unsubstituted or        substituted with one or more substituents, preferably phenyl        substituted with one or more C₁₋₂₀ alkyl groups;    -   a linear or branched chain of aryl or heteroaryl groups, each of        which groups may independently be substituted, for example a        group of formula —(Ar³)_(r) wherein each Ar³ is independently an        aryl or heteroaryl group and r is at least 2, preferably a        branched or linear chain of phenyl groups each of which may be        unsubstituted or substituted with one or more C₁₋₂₀ alkyl        groups; and    -   a crosslinkable-group, for example a group comprising a double        bond such and a vinyl or acrylate group, or a benzocyclobutane        group.

In the case where R³ comprises an aryl or heteroaryl group, or a linearor branched chain of aryl or heteroaryl groups, the or each aryl orheteroaryl group may be substituted with one or more substituents R⁷selected from the group consisting of:

-   -   alkyl, for example C₁₋₂₀ alkyl, wherein one or more non-adjacent        C atoms may be replaced with O, S, substituted N, C═O and —COO—        and one or more H atoms of the alkyl group may be replaced with        F;    -   NR⁹ ₂, OR⁹, SR⁹, SiR⁹ ₃ and    -   fluorine, nitro and cyano;

wherein each R⁹ is independently selected from the group consisting ofalkyl, preferably C₁₋₂₀ alkyl; and aryl or heteroaryl, preferablyphenyl, optionally substituted with one or more C₁₋₂₀ alkyl groups.

Substituted N, where present, may be —NR⁹— wherein R⁹ is as describedabove.

Preferably, each R³, where present, is independently selected from C₁₋₄₀hydrocarbyl, and is more preferably selected from C₁₋₂₀ alkyl;unusubstituted phenyl; phenyl substituted with one or more C₁₋₂₀ alkylgroups; a linear or branched chain of phenyl groups, wherein each phenylmay be unsubstituted or substituted with one or more substituents; and acrosslinkable group.

If n is 1 then exemplary repeat units of formula (III) include thefollowing:

A particularly preferred repeat unit of formula (III) has formula(IIIa):

Substituents R³ of formula (IIIa) are adjacent to linking positions ofthe repeat unit, which may cause steric hindrance between the repeatunit of formula (IIIa) and adjacent repeat units, resulting in therepeat unit of formula (IIIa) twisting out of plane relative to one orboth adjacent repeat units.

Exemplary repeat units where n is 2 or 3 include the following:

A preferred repeat unit has formula (IIIb):

The two R³ groups of formula (IIIb) may cause steric hindrance betweenthe phenyl rings they are bound to, resulting in twisting of the twophenyl rings relative to one another.

A further class of arylene repeat units are optionally substitutedfluorene repeat units, such as repeat units of formula (IV):

wherein R³ in each occurrence is the same or different and is asubstituent as described with reference to formula (III), and whereinthe two groups R³ may be linked to form a ring; R⁸ is a substituent; andd is 0, 1, 2 or 3.

The aromatic carbon atoms of the fluorene repeat unit may beunsubstituted, or may be substituted with one or more substituents R⁸.Exemplary substituents R⁸ are alkyl, for example C₁₋₂₀ alkyl, whereinone or more non-adjacent C atoms may be replaced with O, S, NH orsubstituted N, C═O and —COO—, optionally substituted aryl, optionallysubstituted heteroaryl, alkoxy, alkylthio, fluorine, cyano andarylalkyl. Particularly preferred substituents include C₁₋₂₀ alkyl andsubstituted or unsubstituted aryl, for example phenyl. Optionalsubstituents for the aryl include one or more C₁₋₂₀ alkyl groups.

Substituted N, where present, may be —NR⁵— wherein R⁵ is C₁₋₂₀ alkyl;unsubstituted phenyl; or phenyl substituted with one or more C₁₋₂₀ alkylgroups.

The extent of conjugation of repeat units of formula (IV) to aryl orheteroaryl groups of adjacent repeat units may be controlled by (a)linking the repeat unit through the 3- and/or 6-positions to limit theextent of conjugation across the repeat unit, and/or (b) substitutingthe repeat unit with one or more substituents R⁸ in or more positionsadjacent to the linking positions in order to create a twist with theadjacent repeat unit or units, for example a 2,7-linked fluorenecarrying a C₁₋₂₀ alkyl substituent in one or both of the 3- and6-positions.

The repeat unit of formula (IV) may be an optionally substituted2,7-linked repeat unit of formula (IVa):

Optionally, the repeat unit of formula (IVa) is not substituted in aposition adjacent to the 2- or 7-position. Linkage through the 2- and7-positions and absence of substituents adjacent to these linkingpositions provides a repeat unit that is capable of providing arelatively high degree of conjugation across the repeat unit.

The repeat unit of formula (IV) may be an optionally substituted3,6-linked repeat unit of formula (IVb)

The extent of conjugation across a repeat unit of formula (IVb) may berelatively low as compared to a repeat unit of formula (IVa).

Another exemplary arylene repeat unit has formula (V):

wherein R³, R⁸ and d are as described with reference to formula (III)and (IV) above. Any of the R³ groups may be linked to any other of theR³ groups to form a ring. Aromatic carbon atoms of the repeat unit offormula (V) may be unsubstituted, or may be substituted with one or moresubstituents.

Repeat units of formula (V) may have formula (Va) or (Vb):

Further arylene co-repeat units include: phenanthrene repeat units;naphthalene repeat units; anthracene repeat units; and perylene repeatunits. Each of these arylene repeat units may be linked to adjacentrepeat units through any two of the aromatic carbon atoms of theseunits. Specific exemplary linkages include 9,10-anthracene;2,6-anthracene; 1,4-naphthalene; 2,6-naphthalene; 2,7-phenanthrene; and2,5-perylene. Each of these repeat units may be substituted orunsubstituted, for example substituted with one or more C₁₋₄₀hydrocarbyl groups.

The polymer preferably contains one or more charge-transporting repeatunits. Exemplary charge-transporting repeat units include repeat unitsof materials disclosed in, for example, Shirota and Kageyama, Chem. Rev.2007, 107, 953-1010

Exemplary hole transporting repeat units may be repeat units ofmaterials having a electron affinity of 2.9 eV or lower and anionisation potential of 5.8 eV or lower, preferably 5.7 eV or lower.

Preferred hole-transporting repeat units are (hetero)arylamine repeatunits, including repeat units of formula (VII):

wherein Ar⁸ and Ar⁹ in each occurrence are independently selected fromsubstituted or unsubstituted aryl or heteroaryl, g is greater than orequal to 1, preferably 1 or 2, R¹³ is H or a substituent, preferably asubstituent, and c and d are each independently 1, 2 or 3.

R¹³, which may be the same or different in each occurrence when g>1, ispreferably selected from the group consisting of alkyl, for exampleC₁₋₂₀ alkyl, Ar¹⁰, a branched or linear chain of Ar¹⁰ groups, or acrosslinkable unit that is bound directly to the N atom of formula(VIII) or spaced apart therefrom by a spacer group, wherein Ar¹⁰ in eachoccurrence is independently optionally substituted aryl or heteroaryl.Exemplary spacer groups are C₁₋₂₀ alkyl, phenyl and phenyl-C₁₋₂₀ alkyl.

Any of Ar⁸, Ar⁹ and, if present, Ar¹⁰ in the repeat unit of Formula (IX)may be linked by a direct bond or a divalent linking atom or group toanother of Ar⁸, Ar⁹ and Ar¹⁰. Preferred divalent linking atoms andgroups include O, S; substituted N; and substituted C.

Any of Ar⁸, Ar⁹ and, if present, Ar¹⁰ may be substituted with one ormore substituents. Exemplary substituents are substituents R¹⁰, whereineach R¹⁰ may independently be selected from the group consisting of:

-   -   substituted or unsubstituted alkyl, optionally C₁₋₂₀ alkyl,        wherein one or more non-adjacent C atoms may be replaced with        optionally substituted aryl or heteroaryl, O, S, substituted N,        C═O or —COO— and one or more H atoms may be replaced with F; and    -   a crosslinkable group attached directly to the fluorene unit or        spaced apart therefrom by a spacer group, for example a group        comprising a double bond such and a vinyl or acrylate group, or        a benzocyclobutane group

Preferred repeat units of formula (VII) have formulae 1-3:

In one preferred arrangement, R¹³ is Ar¹⁰ and each of Ar⁸, Ar⁹ and Ar¹⁰are independently and optionally substituted with one or more C₁₋₂₀alkyl groups. Ar⁸, Ar⁹ and Ar¹⁰ are preferably phenyl.

In another preferred arrangement, the central Ar⁹ group of formula (I)linked to two N atoms is a polycyclic aromatic that may be unsubstitutedor substituted with one or more substituents R¹⁰. Exemplary polycyclicaromatic groups are naphthalene, perylene, anthracene and fluorene.

In another preferred arrangement, Ar⁸ and Ar⁹ are phenyl, each of whichmay be substituted with one or more C₁₋₂₀ alkyl groups, and R¹³ is—(Ar¹⁰)_(r) wherein r is at least 2 and wherein the group —(Ar¹⁰)_(r)forms a linear or branched chain of aromatic or heteroaromatic groups,for example 3,5-diphenylbenzene wherein each phenyl may be substitutedwith one or more C₁₋₂₀ alkyl groups. In another preferred arrangement,c, d and g are each 1 and Ar⁸ and Ar⁹ are phenyl linked by an oxygenatom to form a phenoxazine ring.

Amine repeat units may be provided in a molar amount in the range ofabout 0.5 mol % up to about 50 mol %, optionally about 1-25 mol %,optionally about 1-10 mol %.

The polymer may contain one, two or more different repeat units offormula (VII).

Amine repeat units may provide hole-transporting and/or light-emittingfunctionality. Preferred fluorescent light-emitting amine repeat unitsinclude a blue light-emitting repeat unit of formula (VIIa) and a greenlight-emitting repeat unit formula (VIIb):

R¹³ of formula (VIIa) is preferably a hydrocarbyl, preferably C₁₋₂₀alkyl, phenyl that is unsubstituted or substituted with one or moreC₁₋₂₀ alkyl groups, or a branched or linear chain of phenyl groupswherein each said phenyl group is unsubstituted or substituted with oneor more C₁₋₂₀ alkyl groups.

The repeat unit of formula (VIIb) may be unsubstituted or one or more ofthe rings of the repeat unit of formula (VIIb) may be substituted withone or more substituents R¹⁵, preferably one or more C₁₋₂₀ alkyl groups.

Another preferred charge-transporting repeat unit has formula (VIII):

wherein Ar⁸, Ar⁹ and Ar¹⁰ are as described with reference to formula(VII) above, and may each independently be substituted with one or moresubstituents described with reference to Ar⁸, Ar⁹ and Ar¹⁰, and z ineach occurrence is independently at least 1, optionally 1, 2 or 3,preferably 1, and Y is N or CR¹⁴, wherein R¹⁴ is H or a substituent,preferably H or C₁₋₁₀ alkyl. Preferably, Ar⁸, Ar⁹ and Ar¹⁰ of formula(VIII) are each phenyl, each phenyl being optionally and independentlysubstituted with one or more C₁₋₂₀ alkyl groups.

In one preferred embodiment, all 3 groups Y are N.

If all 3 groups Y are CR¹⁴ then at least one of Ar⁸, Ar⁹ and Ar¹⁰ ispreferably a heteroaromatic group comprising N.

Each of Ar⁸, Ar⁹ and Ar¹⁰ may independently be substituted with one ormore substituents. In one arrangement, Ar⁸, Ar⁹ and Ar¹⁰ are phenyl ineach occurrence. Exemplary substituents include R⁵ as described abovewith reference to formula (V), for example C₁₋₂₀ alkyl or alkoxy.

Ar¹⁰ of formula (VIII) is preferably phenyl, and is optionallysubstituted with one or more C₁₋₂₀ alkyl groups or a crosslinkable unit.

Preferably, z is 1 and each of Ar⁸, Ar⁹ and Ar¹⁰ is unsubstituted phenylor phenyl substituted with one or more C₁₋₂₀ alkyl groups.

A particularly preferred repeat unit of formula (VIII) has formula(VIIIa), which may be unsubstituted or substituted with one or moresubstituents R⁵, preferably one or more C₁₋₂₀ alkyl groups:

Light-Emitting Layers

An OLED may contain one or more light-emitting layers. A light-emittinglayer may contain a polymer comprising repeat units of formula (I).

Suitable light-emitting materials for a light-emitting layer includepolymeric, small molecule and dendritic light-emitting materials, eachof which may be fluorescent or phosphorescent.

A light-emitting layer of an OLED may be unpatterned, or may bepatterned to form discrete pixels. Each pixel may be further dividedinto subpixels. The light-emitting layer may contain a singlelight-emitting material, for example for a monochrome display or othermonochrome device, or may contain materials emitting different colours,in particular red, green and blue light-emitting materials for afull-colour display.

A light-emitting layer may contain a mixture of more than onelight-emitting material, for example a mixture of light-emittingmaterials that together provide white light emission.

A white-emitting OLED may contain a single, white-emitting layer or maycontain two or more layers that emit different colours which, incombination, produce white light. The light emitted from awhite-emitting OLED may have CIE x coordinate equivalent to that emittedby a black body at a temperature in the range of 2500-9000K and a CIE ycoordinate within 0.05 or 0.025 of the CIE y co-ordinate of said lightemitted by a black body, optionally a CIE x coordinate equivalent tothat emitted by a black body at a temperature in the range of2700-6000K.

Exemplary fluorescent polymeric light-emitting materials includepolymers comprising one or more of arylene repeat units, arylenevinylene repeat units and arylamine repeat units.

Exemplary phosphorescent light-emitting materials include metalcomplexes. A phosphorescent material may be a material comprising asubstituted or unsubstituted complex of formula (IX):ML¹ _(q)L² _(r)L³ _(s)  (IX)

wherein M is a metal; each of L¹, L² and L³ is a coordinating group; qis a positive integer; r and s are each independently 0 or a positiveinteger; and the sum of (a. q)+(b. r)+(c.s) is equal to the number ofcoordination sites available on M, wherein a is the number ofcoordination sites on L¹, b is the number of coordination sites on L²and c is the number of coordination sites on L³.

Heavy elements M induce strong spin-orbit coupling to allow rapidintersystem crossing and emission from triplet or higher states.Suitable heavy metals M include d-block metals, in particular those inrows 2 and 3 i.e. elements 39 to 48 and 72 to 80, in particularruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum andgold. Iridium is particularly preferred.

Exemplary ligands L¹, L² and L³ include carbon or nitrogen donors suchas porphyrin or bidentate ligands of formula (X):

wherein Ar⁵ and Ar⁶ may be the same or different and are independentlyselected from substituted or unsubstituted aryl or heteroaryl; X¹ and Y¹may be the same or different and are independently selected from carbonor nitrogen; and Ar⁵ and Ar⁶ may be fused together. Ligands wherein X¹is carbon and Y¹ is nitrogen are preferred, in particular ligands inwhich Ar⁵ is a single ring or fused heteroaromatic of N and C atomsonly, for example pyridyl or isoquinoline, and Ar⁶ is a single ring orfused aromatic, for example phenyl or naphthyl.

To achieve red emission, Ar⁵ may be selected from phenyl, fluorene,naphthyl and Ar⁶ are selected from quinoline, isoquinoline, thiopheneand benzothiophene.

To achieve green emission, Ar⁵ may be selected from phenyl or fluoreneand Ar⁶ may be pyridine.

To achieve blue emission, Ar⁵ may be selected from phenyl and Ar⁶ may beselected from imidazole, pyrazole, triazole and tetrazole.

Examples of bidentate ligands are illustrated below:

Each of Ar⁵ and Ar⁶ may carry one or more substituents. Two or more ofthese substituents may be linked to form a ring, for example an aromaticring.

Other ligands suitable for use with d-block elements includediketonates, in particular acetylacetonate (acac),tetrakis-(pyrazol-1-yl)borate, 2-carboxypyridyl, triarylphosphines andpyridine, each of which may be substituted.

Exemplary substituents include groups R¹³ as described above withreference to Formula (VII). Particularly preferred substituents includefluorine or trifluoromethyl which may be used to blue-shift the emissionof the complex, for example as disclosed in WO 02/45466, WO 02/44189, US2002-117662 and US 2002-182441; alkyl or alkoxy groups, for exampleC₁₋₂₀ alkyl or alkoxy, which may be as disclosed in JP 2002-324679;carbazole which may be used to assist hole transport to the complex whenused as an emissive material, for example as disclosed in WO 02/81448;and dendrons which may be used to obtain or enhance solutionprocessability of the metal complex, for example as disclosed in WO02/66552.

A light-emitting dendrimer typically comprises a light-emitting corebound to one or more dendrons, wherein each dendron comprises abranching point and two or more dendritic branches. Preferably, thedendron is at least partially conjugated, and at least one of thebranching points and dendritic branches comprises an aryl or heteroarylgroup, for example a phenyl group. In one arrangement, the branchingpoint group and the branching groups are all phenyl, and each phenyl mayindependently be substituted with one or more substituents, for examplealkyl or alkoxy.

A dendron may have optionally substituted formula (XI)

wherein BP represents a branching point for attachment to a core and G₁represents first generation branching groups.

The dendron may be a first, second, third or higher generation dendron.G₁ may be substituted with two or more second generation branchinggroups G₂, and so on, as in optionally substituted formula (XIa):

wherein u is 0 or 1; v is 0 if u is 0 or may be 0 or 1 if u is 1; BPrepresents a branching point for attachment to a core and G₁, G₂ and G₃represent first, second and third generation dendron branching groups.In one preferred embodiment, each of BP and G₁, G₂ . . . G_(n) isphenyl, and each phenyl BP, G₁, G₂ . . . G_(n−1) is a 3,5-linked phenyl.

A preferred dendron is a substituted or unsubstituted dendron of formula(XIb):

wherein * represents an attachment point of the dendron to a core.

BP and/or any group G may be substituted with one or more substituents,for example one or more C₁₋₂₀ alkyl or alkoxy groups.

Phosphorescent light-emitting materials may be provided in alight-emitting layer with a host material. The host material may be ahost polymer of the invention.

The phosphorescent light-emitting material may be physically mixed withthe host polymer or may be covalently bound thereto. The phosphorescentlight-emitting material may be provided in a side-chain, main chain orend-group of the polymer. Where the phosphorescent material is providedin a polymer side-chain, the phosphorescent material may be directlybound to the backbone of the polymer or spaced apart therefrom by aspacer group, for example a C₁₋₂₀ alkyl spacer group in which one ormore non-adjacent C atoms may be replaced by O or S. It will thereforebe appreciated that a composition of the present invention may consistof or may comprise a polymer of the invention comprising repeat units offormula (I) with a phosphorescent light-emitting material bound to thepolymer.

In the case where one or more phosphorescent light-emitting materialsare mixed with a host material, the phosphorescent light-emittingmaterial(s) may make up about 0.05 wt % up to about 50 wt %, optionallyabout 1-40 wt % of a host/phosphorescent light-emitting materialcomposition.

In the case where one or more phosphorescent light-emitting materialsare bound to a host material, for example a host polymer, thephosphorescent light-emitting material(s) may make up about 0.01-25 mol% of the material.

Charge Transporting and Charge Blocking Layers

In the case of an OLED, a hole transporting layer may be providedbetween the anode and the light-emitting layer or layers. Likewise, anelectron transporting layer may be provided between the cathode and thelight-emitting layer or layers.

Similarly, an electron blocking layer may be provided between the anodeand the light-emitting layer and a hole blocking layer may be providedbetween the cathode and the light-emitting layer. Transporting andblocking layers may be used in combination. Depending on its HOMO andLUMO levels, a single layer may both transport one of holes andelectrons and block the other of holes and electrons.

A charge-transporting layer or charge-blocking layer may be crosslinked,particularly if a layer overlying that charge-transporting orcharge-blocking layer is deposited from a solution. The crosslinkablegroup used for this crosslinking may be a crosslinkable group comprisinga reactive double bond such and a vinyl or acrylate group, or abenzocyclobutane group.

If present, a hole transporting layer located between the anode and thelight-emitting layers preferably has a HOMO level of less than or equalto 5.5 eV, more preferably around 4.8-5.5 eV or 5.1-5.3 eV as measuredby cyclic voltammetry. The HOMO level of the hole transport layer may beselected so as to be within 0.2 eV, optionally within 0.1 eV, of anadjacent layer (such as a light-emitting layer) in order to provide asmall barrier to hole transport between these layers.

If present, an electron transporting layer located between thelight-emitting layers and cathode preferably has a LUMO level of around2.5-3.5 eV as measured by cyclic voltammetry. For example, a layer of asilicon monoxide or silicon dioxide or other thin dielectric layerhaving thickness in the range of 0.2-2 nm may be provided between thelight-emitting layer nearest the cathode and the cathode. HOMO and LUMOlevels may be measured using cyclic voltammetry.

A hole transporting layer may contain a homopolymer or copolymercomprising a repeat unit of formula (VII) as described above, forexample a copolymer comprising one or more amine repeat units of formula(VII) and one or more arylene repeat units, for example one or morearylene repeat units selected from formulae (III), (IV) and (V).

An electron transporting layer may contain a polymer comprising a chainof optionally substituted arylene repeat units, such as a chain offluorene repeat units.

If a hole- or electron-transporting layer is adjacent a light-emittinglayer containing a phosphorescent material then the T₁ energy level ofthe material or materials of that layer are preferably higher than thatof the phosphorescent emitter in the adjacent light-emitting layer.

Hole Injection Layers

A conductive hole injection layer, which may be formed from a conductiveorganic or inorganic material, may be provided between the anode 101 andthe light-emitting layer 103 of an OLED as illustrated in FIG. 1 toassist hole injection from the anode into the layer or layers ofsemiconducting polymer. Examples of doped organic hole injectionmaterials include optionally substituted, doped poly(ethylenedioxythiophene) (PEDT), in particular PEDT doped with a charge-balancingpolyacid such as polystyrene sulfonate (PSS) as disclosed in EP 0901176and EP 0947123, polyacrylic acid or a fluorinated sulfonic acid, forexample Nafion®; polyaniline as disclosed in U.S. Pat. No. 5,723,873 andU.S. Pat. No. 5,798,170; and optionally substituted polythiophene orpoly(thienothiophene). Examples of conductive inorganic materialsinclude transition metal oxides such as VOx, MoOx and RuOx as disclosedin Journal of Physics D: Applied Physics (1996), 29(11), 2750-2753.

Cathode

The cathode 105 is selected from materials that have a workfunctionallowing injection of electrons into the light-emitting layer of theOLED. Other factors influence the selection of the cathode such as thepossibility of adverse interactions between the cathode and thelight-emitting material. The cathode may consist of a single materialsuch as a layer of aluminum. Alternatively, it may comprise a pluralityof conductive materials such as metals, for example a bilayer of a lowworkfunction material and a high workfunction material such as calciumand aluminum, for example as disclosed in WO 98/10621. The cathode maycomprise elemental barium, for example as disclosed in WO 98/57381,Appl. Phys. Lett. 2002, 81(4), 634 and WO 02/84759. The cathode maycomprise a thin (e.g. 1-5 nm) layer of metal compound, in particular anoxide or fluoride of an alkali or alkali earth metal, between theorganic layers of the device and one or more conductive cathode layersto assist electron injection, for example lithium fluoride as disclosedin WO 00/48258; barium fluoride as disclosed in Appl. Phys. Lett. 2001,79(5), 2001; and barium oxide. In order to provide efficient injectionof electrons into the device, the cathode preferably has a workfunctionof less than 3.5 eV, more preferably less than 3.2 eV, most preferablyless than 3 eV. Work functions of metals can be found in, for example,Michaelson, J. Appl. Phys. 48(11), 4729, 1977.

The cathode may be opaque or transparent. Transparent cathodes areparticularly advantageous for active matrix devices because emissionthrough a transparent anode in such devices is at least partiallyblocked by drive circuitry located underneath the emissive pixels. Atransparent cathode comprises a layer of an electron injecting materialthat is sufficiently thin to be transparent. Typically, the lateralconductivity of this layer will be low as a result of its thinness. Inthis case, the layer of electron injecting material is used incombination with a thicker layer of transparent conducting material suchas indium tin oxide.

It will be appreciated that a transparent cathode device need not have atransparent anode (unless, of course, a fully transparent device isdesired), and so the transparent anode used for bottom-emitting devicesmay be replaced or supplemented with a layer of reflective material suchas a layer of aluminum. Examples of transparent cathode devices aredisclosed in, for example, GB 2348316.

Encapsulation

Organic optoelectronic devices tend to be sensitive to moisture andoxygen. Accordingly, the substrate preferably has good barrierproperties for prevention of ingress of moisture and oxygen into thedevice. The substrate is commonly glass, however alternative substratesmay be used, in particular where flexibility of the device is desirable.For example, the substrate may comprise one or more plastic layers, forexample a substrate of alternating plastic and dielectric barrier layersor a laminate of thin glass and plastic.

The device may be encapsulated with an encapsulant (not shown) toprevent ingress of moisture and oxygen. Suitable encapsulants include asheet of glass, films having suitable barrier properties such as silicondioxide, silicon monoxide, silicon nitride or alternating stacks ofpolymer and dielectric or an airtight container. In the case of atransparent cathode device, a transparent encapsulating layer such assilicon monoxide or silicon dioxide may be deposited to micron levels ofthickness, although in one preferred embodiment the thickness of such alayer is in the range of 20-300 nm. A getter material for absorption ofany atmospheric moisture and/or oxygen that may permeate through thesubstrate or encapsulant may be disposed between the substrate and theencapsulant.

Formulation Processing

A formulation suitable for forming a charge-transporting orlight-emitting layer may be formed from the polymer of the invention,any further components of the layer such as light-emitting dopants, andone or more suitable solvents.

The formulation may be a solution of the polymer and any othercomponents in the one or more solvents, or may be a dispersion in theone or more solvents in which one or more components are not dissolved.Preferably, the formulation is a solution.

Solvents suitable for dissolving semiconducting polymers, particularlypolymers comprising alkyl substituents, include benzenes substitutedwith one or more C₁₋₁₀ alkyl or C₁₋₁₀ alkoxy groups, for exampletoluene, xylenes and methylanisoles.

A charge-transporting or light-emitting layer of an OLED may be formedby depositing the formulation containing a polymer as described hereinand evaporating the one or more solvents.

Particularly preferred solution deposition techniques including printingand coating techniques such spin-coating and inkjet printing.

Spin-coating is particularly suitable for devices wherein patterning ofthe light-emitting layer is unnecessary—for example for lightingapplications or simple monochrome segmented displays.

Inkjet printing is particularly suitable for high information contentdisplays, in particular full colour displays. A device may be inkjetprinted by providing a patterned layer over the first electrode anddefining wells for printing of one colour (in the case of a monochromedevice) or multiple colours (in the case of a multicolour, in particularfull colour device). The patterned layer is typically a layer ofphotoresist that is patterned to define wells as described in, forexample, EP 0880303.

As an alternative to wells, the ink may be printed into channels definedwithin a patterned layer. In particular, the photoresist may bepatterned to form channels which, unlike wells, extend over a pluralityof pixels and which may be closed or open at the channel ends.

Other solution deposition techniques include dip-coating, roll printingand screen printing.

EXAMPLES Synthesis of Monomer Example 1

Stage 1

An oven-dried 3 L 4-neck flask fitted with an internal thermometer, N2bubbler, overhead stirrer and oven-dried mL pressure-equalising droppingfunnel was charged with 1,4-dibromo-2,5-diethylbenzene (70 g, 240 mmol)and dry THF (700 mL). The solution was cooled with stirring to <−70° C.to produce a white slurry. s-Butyllithium (335 mL, 1.4 M, 465 mmol) wascharged to the dropping funnel and added dropwise over the space of 1.5h ensuring the reaction temperature did not exceed −70° C. The slurrywas stirred for 3 h after which GCMS confirmed the lithiation wascomplete. The dropping funnel was charged with a solution of1,4-diiodobutane (13.8 mL, 105 mmol) in dry THF (140 mL) which was thenadded dropwise over 0.75 h. The resulting slurry was allowed to warm toroom temperature and stirred for 12 h. The reaction was quenched byaddition of water. The mixture was transferred to a separating funneland the layers were separated. The aqueous layer was extracted withdiethyl ether and the combined organics were washed with water, driedwith MgSO₄, filtered and concentrated to yield an orange oil. Theproduct was triturated with 500 mL methanol for 0.5 h and filtered as awhite solid before being recrystallised from toluene/IPA to yield awhite powder that was dried in the oven (24.21 g, 48%). GCMS indicated apurity of ˜96% and the material was taken to the next stage withoutfurther purification

Stage 2

An oven-dried 2 L 4-neck flask fitted with an internal thermometer, N2bubbler, overhead stirrer and oven-dried mL pressure-equalising droppingfunnel was charged with Stage 1 material (45 g, 94 mmol) and dry THF(450 mL). The solution was cooled with stirring to <−70° C. to produce awhite slurry. n-Butyllithium (96 mL, 2.5 M, 225 mmol) was charged to thedropping funnel and added dropwise over the space of 0.75 h ensuring thereaction temperature did not exceed −70° C. The slurry was stirred for 5h after which GCMS confirmed the lithiation was complete. The droppingfunnel was charged with a solution of IPPB (50 mL, 235 mmol) in dry THF(100 mL) which was then added dropwise over 0.75 h. The resulting slurrywas allowed to warm to room temperature and stirred for 12 h. Thereaction was quenched by addition of HCl in ether. The solvent wasremoved, diethyl ether added, the mixture was transferred to aseparating funnel and the layers were separated. The aqueous layer wasextracted with diethyl ether and the combined organics were washed withwater, dried with MgSO₄, filtered and concentrated to yield an orangeoil. The product was triturated with 500 mL acetonitrile for 1 h in anice-bath and filtered as a white solid before being recrystallised fromacetonitrile to yield a white powder. The solid was dissolved in a 2:1(v/v) mixture of DCM and hexanes and passed through a plug of Florisil®(diameter 11 cm, height 4 cm) on silica (diameter 11 cm, height 7 cm)and then recrystallised from acetonitrile three times to give a whitepowder which was filtered and dried in the oven (13 g, 24%). HPLCindicated a purity of 99.67%

¹H NMR (referenced to CDCl₃ peak at 7.26 ppm): 7.57 (2H, s), 6.98 (2H,s), 2.84-2.88 (4H, m), 2.61-2.64 (8H, m), 1.67 (4H, m), 1.32 (24H, s),1.17-1.21 (12H, m)

Synthesis of Monomer Example 2

Stage 1

An oven-dried 3 L 4-neck flask fitted with an internal thermometer, N2bubbler, overhead stirrer and oven-dried pressure-equalising droppingfunnel was charged with 1,4-dibromo-2,5-dimethylbenzene (70 g, 265 mmol)and dry THF (700 mL). The solution was cooled with stirring to <−70° C.to produce a white slurry. s-Butyllithium (370 mL, 1.4 M, 518 mmol) wascharged to the dropping funnel and added dropwise over the space of 2 hensuring the reaction temperature did not exceed −70° C. The slurry wasstirred for 2 h after which GCMS confirmed the lithiation was complete.The dropping funnel was charged with a solution of 1,4-diiodobutane(15.7 mL, 119 mmol) in dry THF (160 mL) which was then added dropwiseover 0.75 h. The resulting pale yellow slurry was allowed to warm toroom temperature and stirred for 12 h. The reaction was quenched byaddition of water. The mixture was transferred to a separating funneland the layers were separated. The aqueous layer was extracted withdiethyl ether and the combined organics were washed with water, driedwith MgSO₄, filtered and concentrated to yield an off-white solid. Theproduct was triturated with 300 mL methanol for 2 h and recrystallisedfrom toluene/IPA to yield a white powder that was dried in the oven(31.86 g, 63%). GCMS indicated a purity of ˜96% and the material wastaken to the next stage without further purification

Stage 2

An oven-dried 2 L 4-neck flask fitted with an internal thermometer, N2bubbler, overhead stirrer and oven-dried pressure-equalising droppingfunnel was charged with Stage 1 material (31.5 g, 74 mmol) and dry THF(350 mL). The solution was cooled with stirring to <−70° C. to produce awhite slurry. n-Butyllithium (62 mL, 2.5 M, 155 mmol) was charged to thedropping funnel and added dropwise over the space of 0.5 h ensuring thereaction temperature did not exceed −70° C. The slurry was stirred for4.5 h. The dropping funnel was charged with a solution of iPPB (33 mL,161 mmol) in dry THF (60 mL) which was then added dropwise over 0.5 h.The resulting slurry was allowed to warm to room temperature and stirredfor 12 h. The reaction was quenched by addition of HCL in ether. The THFwas removed, diethyl ether added, the mixture was transferred to aseparating funnel and the layers were separated. The aqueous layer wasextracted with diethyl ether and the combined organics were washed withwater, dried with MgSO₄, filtered and concentrated to yield a whitesolid. The product was triturated with 500 mL methanol for 0.5 h. Thefiltered solid was purified by chromatography on silica using a gradientof DCM in hexanes as the eluant. The product-containing fractions wereconcentrated and recrystallised from acetonitrile to yield a whitepowder that was dried in the oven (20.44 g, 53%). HPLC indicated thepurity was 99.77%

¹H NMR (referenced to CDCl₃ peak at 7.26 ppm): 7.53 (2H, s), 6.93 (2H,s), 2.59 (4H, m), 2.47 (6H, s), 2.26 (6H, s), 1.62 (4H, m), 1.33 (24H,s)

Host Polymer Examples

Polymers were prepared by Suzuki polymerisation as described in WO00/53656 of a polymerisation mixture containing the molar percentages ofmonomers given in Table 1.

TABLE 1 Viscosity Weight Peak Number average average average averageDiester Dihalo molecular molecular molecular molecular monomer monomersweight weight weight weight Polymer (mol %) (mol %) (Mz) (Mw) (Mp) (Mn)Pd Polymer Monomer 3 (5)  1,280,000 630,000 770,000 21,000 30.00 Example1 Example 1 4 (45) (50) Polymer Monomer 3 (9)  111,000 64,000 71,00015,000 4.16 Example 2 Example 2 4 (41) (50) Comparative Comparative 6(50) 455,000 256,000 224,000 96,000 2.78 Polymer 1 Monomer 1 (50)Comparative Monomer 7 Comparative 571,000 235,000 177,000 17,600 13.40Polymer 2 (50) Monomer 2 (50) Comparative 7 (50)  6 (28.5) Polymer 3  3(21.5) Polymer Monomer 4 (25) Example 3 Example 1 3 (25) (50) PolymerMonomer 4 (10) Example 4 Example 1 3 (40) (50) Polymer Monomer 4 (35)Example 5 Example 1 10 (15)  (50) Polymer Monomer 4 (30) Example 6Example 1 11 (20)  (50) Polymer Monomer 4 (32) Example 7 Example 1 12(18)  (50) Polymer Monomer 4 (32) Example 8 Example 1 13 (18)  (50)Comparative 9 (50) 3 (5)  Polymer 4 4 (45)

Monomer 12 is described in JP2012-137538. Monomer 10 is described inJP2012-137537.

Polymer Example 1 includes the following repeating structures:

Polymer Example 2 includes the following repeating structures:

Comparative Polymer 1 includes the following repeating structure:

Monomer 8 (Comparative Monomer 2) was prepared as described in WO2011/141714. Comparative Polymer 2 includes the following repeatingstructure:

Comparative Polymer 3 includes the following repeating structures:

Comparative Polymer 4 includes the following repeating structures:

Composition Examples

A composition of 95 mol % of a polymer as described above and 5 mol % ofBlue Phosphorescent Emitter 1, illustrated below, was dissolved ino-xylene and cast as a film by spin-coating.

Blue Phosphorescent Emitter 1

The core of Blue Phosphorescent Emitter 1 is disclosed in WO2004/101707.Formation of dendrons is described in WO 02/066552.

Synthesis of Blue Phosphorescent Emitter 1

Stage 1:

fac-Tris(1-methyl-5-phenyl-3-propyl-[1,2,4]triazolyl)iridium-(III) (1.1g) (Shih-Chun Lo et al., Chem. Mater. 2006, 18, 5119-5129) (1.1 g) wasdissolved in DCM (100 mL) under a flow of nitrogen. N-Bromosuccinimide(0.93 g) was added as a solid and the mixture was stirred at roomtemperature with protection from light. After 24 h HPLC analysis showed˜94% product and ˜6% dibromide intermediate.

A further 50 mg of NBS was added and stirring continued for 16 hours. Afurther 50 mg of NBS was added and stirring continued for 24 h. HPLCindicated over 99% product. Warm water was added and stirred for 0.5 h.The layers were separated and the organic layer passed through a plug ofcelite eluting with DCM. The filtrate was concentrated to ˜15 mL andhexane was added to the DCM solution to precipitate the product as ayellow solid in 80% yield.

Stage 2:

Stage 1 material (8.50 g) and3,5-bis(4-tert-butylphenyl)phenyl-1-boronic acid pinacol ester (15.50 g)were dissolved in toluene (230 mL). The solution was purged withnitrogen for 1 h before 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl(66 mg) and tris(dibenzylidene)dipalladium (75 mg) were added using 10mL of nitrogen-purged toluene. A 20 wt % solution of tetraethylammoniumhydroxide in water (60 mL) was added in one portion and the mixture asstirred for 20 h with the heating bath set to 105° C. T.L.C. analysisindicated all the stage material had been consumed and only onefluorescent spot was observed. The reaction mixture was cooled andfiltered into a separating funnel. The layers were separated and theaqueous layer extracted with toluene. The organic extracts were washedwith water, dried with magnesium sulphate, filtered and concentrated toyield the crude product as a yellow/orange solid. Pure compound wasobtained by column chromatography eluting with a gradient of ethylacetate in hexanes followed by precipitation from DCM/methanol. HPLCindicated a purity of 99.75% and a yield of 80% (11.32 g). 1H NMR(referenced to CDCl3): 7.83 (3H, d), 7.76 (6H, s), 7.73 (3H, s) 7.63(12H, d) 7.49 (12H, d), 7.21 (3H, dd), 6.88 (3H, d), 4.28 (9H, s), 2.25(3H, m), 1.98 (3H, m), 1.4-1.5 (57H, m), 1.23 (3H, m), 0.74 (9H, t)

With reference to Table 2, it can be seen that photoluminescent quantumyield (PLQY) of the films are comparable for compositions containingPolymer Example 1 and Comparative Polymer 2, whereas the PLQY values ofcompositions containing Comparative Polymers 1 and 3 are much lower.Without wishing to be bound by any theory, it is believed that theextended conjugation between adjacent phenyl groups in the backbones ofComparative Polymers 1, 3 and 4 results in a low triplet energy leveland quenching of phosphorescence.

TABLE 2 Polymer PLQY (%) CIE x CIE y Polymer Example 1 63 0.158 0.308Comparative 7 0.189 0.173 Polymer 1 Comparative 76 0.157 0.299 Polymer 2Comparative 15 0.177 0.307 Polymer 3 Comparative 6 0.156 0.302 Polymer 4

Green Device Examples

Organic light-emitting devices having the following structure wereprepared:

ITO/HIL/HTL/LE/Cathode

wherein ITO is an indium-tin oxide anode; HIL is a hole-injecting layer;HTL is a hole-transporting layer; LE is a light-emitting layer; and thecathode comprises a layer of metal fluoride in contact with thelight-emitting layer and a layer of aluminum formed over the layer ofmetal fluoride.

To form the device, a substrate carrying ITO was cleaned using UV/Ozone.The hole injection layer was formed by spin-coating an aqueousformulation of a hole-injection material available from Plextronics,Inc. A hole transporting layer was formed to a thickness of 20 nm byspin-coating Hole-Transporting Polymer 1 and crosslinking the polymer byheating. A light-emitting layer was formed by depositing alight-emitting composition of a host polymer (65 wt %) and GreenPhosphorescent Emitter 1, illustrated below (35 wt %), by spin-coatingfrom o-xylene solution a thickness of 75 nm. Green PhosphorescentEmitter 1 is a dendrimeric phosphorescent emitter, as described in WO02/066552. A cathode was formed by evaporation of a first layer of ametal fluoride to a thickness of about 2 nm, a second layer of aluminumto a thickness of about 200 nm and a third layer of silver.

Green Phosphorescent Emitter 1

Hole-Transporting Polymer 1 was formed by Suzuki polymerisation asdescribed in WO 00/53656 of the following monomers:

With reference to Table 3, it can be seen that devices containingPolymer Examples 1 and 2 as host polymer both reach a brightness of 1000cd/m² at a lower voltage; have higher conductivity as shown by thevoltage required to reach a current of 10 mA/cm²; and are more efficientthan a device containing Comparative Polymer 2 as host polymer.

Performance of devices containing Polymer Examples 1 and 2 is comparableto performance of the device containing Comparative Polymer 3.

TABLE 3 Efficiency Efficiency EQE at Max V at J at V at Lm/W at Cd/A at1 kcd/m² EQE Polymer 1 kcd/m² 1 kcd/m² 10 mA/cm² 1 kcd/m² 1 kcd/m2 (%)(%) Polymer 4.75 1.3 6.78 49.16 74.63 20.68 21.31 Example 1 Polymer 4.451.4 6.48 50.59 72.48 20.02 20.52 Example 2 Comparative 5.46 1.6 7.3736.12 62.5 17.39 17.58 Polymer 2 Comparative 4.44 1.4 6.19 50.93 71.8519.8 20.68 Polymer 3

The time taken for brightness of these devices to fall to 70% (T70) andto 50% (T50) of a starting luminance of 5,000 cd/m² is shown in Table 4.Polymer Examples 1 and 2 both have higher lifetimes than ComparativePolymer 2. The lifetime of Comparative Polymer 3 is slightly higher thanPolymer Examples 1 or 2, but this polymer gives poor efficiency whenused with a blue phosphorescent emitter, as shown in Table 2 above.

TABLE 4 T70 T50 J Host polymer (hours (hours) (mA/cm²) ComparativePolymer 2 2.67 10.31 7.63 Polymer Example 1 5.12 21.80 7.08 PolymerExample 2 4.81 24.96 6.77 Comparative Polymer 3 6.33 30.17 6.99

Blue Device Example 1

A device was prepared as described for the green device examples aboveexcept that the light-emitting layer was formed by spin-coating amixture of Polymer Example 1 and Blue Phosphorescent Emitter 1 (36 mol%)

Comparative Blue Device 1

A device was prepared as described in Blue Device Example 1, except thatPolymer Example 1 was replaced with Comparative Polymer 2.

Blue Device Example 2

A device containing a light-emitting layer of a mixture of PolymerExample 1 and Blue Phosphorescent Emitter 1 (36 wt %) was prepared asdescribed for the green device examples above. The hole-transportinglayer was formed by Suzuki polymerization of the following monomers, asdescribed in WO 00/53656:

Comparative Blue Device 2

A device was prepared as described in Blue Device Example 2, except thatPolymer Example 1 was replaced with Comparative Polymer 2.

Data for blue devices are provided in Table 5, in which T70 and T50 arethe time taken for luminance to fall to 70% and 50% respectively of astarting luminance.

TABLE 5 J Eff. Eff. Max V at (mA/cm²) at V at (Lm/W) at (Cd/A) at EQE atEQE T70 T50 Device 1000 cd/m² 1000 cd/m2 10 mA/cm² 1 kcd/m2 1 kcd/m2 1kcd/m² (%) (%) (hours) (hours) Comparative 6.34 3.2 7.61 15.38 31.0217.52 19.04 2.05 8.41 Blue Device 1 Blue 6.11 3.6 7.28 14.13 27.53 13.4315.91 1.13 5.60 Device Example 1 Blue 5.79 7.8 6 6.98 12.88 5.86 6.1414.52 36.66 Device Example 2 Comparative 5.91 7.4 6.19 7.05 13.42 7.878.47 7.91 25.99 Blue Device 2

The polymers of the invention are more conductive than the comparativepolymers, as is shown by the higher current density values for theinventive polymers.

White Devices—General Process

Organic light-emitting devices having the following structure wereprepared:

ITO/HIL/HTL/LEL/Cathode

wherein ITO is an indium-tin oxide anode; HIL is a hole-injecting layercomprising a hole-injecting material, HTL is a hole-transporting layer,and LEL is a light-emitting layer containing a metal complex and a hostpolymer and formed by spin-coating.

A substrate carrying ITO was cleaned using UV/Ozone. A hole injectionlayer was formed to a thickness of about 35 nm by spin-coating anaqueous formulation of a hole-injection material available fromPlextronics, Inc. A hole transporting layer was formed to a thickness ofabout 22 nm by spin-coating Hole-Transporting Polymer 1 and crosslinkingthe polymer by heating. A light-emitting layer was formed by depositinga light-emitting composition containing a host polymer doped with red,green and blue light-emitting metal complexes to a thickness of about 75nm by spin-coating. A cathode was formed by evaporation of a first layerof a sodium fluoride to a thickness of about 2 nm, a second layer ofaluminum to a thickness of about 100 nm and a third layer of silver to athickness of about 100 nm.

The blue light-emitting metal complex was complex selected from BluePhosphorescent Emitter 1 and Blue Phosphorescent Emitter 2; the greenemitting metal complex was Green Phosphorescent Emitter 1 describedabove; and the red-emitting metal complex was Red Phosphorescent Emitter1, as described in WO/2012/153082.

The composition of white device examples and comparative white devicesis provided in Table 6.

TABLE 6 Light-emitting layer Host Blue composition V at J at V atpolymer emitter (wt %) 1 kcd/m2 1 kcd/m2 10 mA/cm2 White Polymer Blue 153:45:1:1 5.87 3.50 6.8 Device Example 3 Example 1 ComparativeComparative Blue 1 53:45:1:1 6.71 3.7 7.69 White Polymer 2 Device 1White Polymer Blue 2 63:35:1:1 5.87 3.30 6.9 Device Example 3 Example 2Comparative Comparative Blue 2 63:35:1:1 7.22 3.3 8.59 White Polymer 2Device 2

The light-emitting layer composition given in Table 6 is the HostPolymer:Blue Emitter:Green Emitter:Red Emitter ratio.

Table 6 shows that devices of the invention have higher conductivitythan the comparative devices.

Hole-Transporting Polymer Examples

Hole-transporting polymers of the invention containing repeat units offormula (I) and hole-transporting amine repeat units, and comparativehole-transporting polymers, were prepared by Suzuki polymerisation asdescribed in WO 00/53656 using monomers as shown in Table 7.

TABLE 7 Viscosity Weight Peak Number average average average averageDiester Dihalo molecular molecular molecular molecular monomer monomersweight weight weight weight Polymer (mol %) (mol %) (Mz) (Mw) (Mp) (Mn)Pd Polymer Monomer 15 (42.5) 498,000 243,000 243,000 16,000 14.83Example 10 Example 1 16 (7.5)  (50) Comparative 7 (50) 15 (42.5) 403,000224,000 215,000 43,000 5.22 Polymer 10 16 (7.5)  Polymer Monomer 17(42.5) 367,000 187,000 182,000 108,000 9.08 Example 11 Example 1 16(7.5)  (50) Comparative 7 (50) 17 (40)  352,000 147,000 118,000 15,00010.08 Polymer 11 18 (5)   19 (5)  

Energy Levels

Polymer Example 10 has a HOMO level of 5.14 eV and a LUMO level of about1.9 eV as measured by cyclic voltammetry.

Polymer Example 11 has a HOMO level of 5.05 eV and a LUMO level of about1.9 eV as measured by cyclic voltammetry.

Photoluminescence Measurements—Phosphorescent Green Blends

A 95:5 weight % composition of Polymer Example 10 and GreenPhosphorescent Emitter 1 was dissolved in mixed xylenes and cast byspin-coating on a glass substrate. For the purpose of comparison, acomparative composition containing Comparative Polymer 10 in place ofPolymer Example 10 was cast in the same way.

With reference to Table 8, photoluminescence quantum yield (PLQY) forthe exemplary composition is much higher than that of the comparativecomposition, indicating that the exemplary polymer causes little or noquenching of phosphorescence of the green phosphorescent emitter. Thisindicates that the exemplary hole-transporting polymers may be used ashole-transporting materials of a hole-transporting layer without causingsignificant quenching of phosphorescence from an adjacent light-emittinglayer.

TABLE 8 Polymer PLQY/% CIE X CIE Y Comparative 48 0.296 0.629 Polymer 10Polymer 74 0.291 0.635 Example 10

Photoluminescence Measurements—Phosphorescent Blue Blends

A 95:5 weight % composition of Polymer Example 11 and BluePhosphorescent Emitter 1 was dissolved in mixed xylenes and cast byspin-coating on a glass substrate. For the purpose of comparison, acomparative composition containing Comparative Polymer 11 in place ofPolymer Example 11 was cast in the same way.

With reference to Table 9, photoluminescence quantum yield (PLQY) forthe exemplary composition is much higher than that of the comparativecomposition, indicating that the exemplary polymer causes little or noquenching of phosphorescence of the blue phosphorescent emitter. Thisindicates that the exemplary hole-transporting polymers may be used ashole-transporting materials of a hole-transporting layer without causingsignificant quenching of phosphorescence from an adjacent light-emittinglayer.

TABLE 9 Polymer PLQY/% CIE X CIE Y Comparative 7 0.169 0.115 Polymer 11Polymer 42 0.157 0.285 Example 11

Blue Device Example 3

A blue light-emitting device was prepared as described for the GreenDevice Examples, except that the hole-transporting layer was formed byspin-coating and cross-linking Polymer Example 10 and the light-emittinglayer was formed by spin-coating Polymer Example 1 (55 weight %) andBlue Phosphorescent Emitter 1 (45 weight %). The device emitted lighthaving a peak at 473 nm.

Blue Device Example 4

A blue light-emitting device was prepared as described for the BlueDevice Example 3, except that Polymer Example 11 was used to form thehole-transporting layer. The device emitted light having a peak at 476nm.

Although the present invention has been described in terms of specificexemplary embodiments, it will be appreciated that variousmodifications, alterations and/or combinations of features disclosedherein will be apparent to those skilled in the art without departingfrom the scope of the invention as set forth in the following claims.

The invention claimed is:
 1. A composition comprising a polymer and atleast one light-emitting dopant, the polymer comprising repeat units offormula (I) and one or more co-repeat units:

Ar¹ in each occurrence independently represents an aryl or heteroarylgroup; R¹ and R² are independently, in each occurrence, C₁₋₄₀hydrocarbyl, —OR¹¹, —SR¹¹, —N(R¹¹)₂, or —Si(R¹¹)₃, wherein R¹¹ in eachoccurrence is a C₁₋₄₀ hydrocarbyl; p independently in each occurrence is0 or a positive integer; Sp represents a C₁₋₂₀ alkyl chain spacer groupwherein one or more non-adjacent C atoms of the chain may be replacedwith O, S, —NR¹¹, —Si(R⁴)₂—, —C(═O)— or —COO— and wherein R⁴ in eachoccurrence is independently H or a C₁₋₄₀ hydrocarbyl group, with theproviso that Sp contains at least one sp³-hybridized carbon atomseparating the two Ar¹ groups; and each group Ar¹ is bound to anaromatic group of a co-repeat unit; wherein the light-emitting dopant isa phosphorescent dopant having a photoluminescent spectrum with a peakin the range of 400-490 nm.
 2. A composition according to claim 1wherein Ar¹ is an aryl group and the Ar¹ groups may be the same ordifferent.
 3. A composition according to claim 2 wherein each Ar¹ isphenyl.
 4. A composition according to claim 3 wherein the repeat unit offormula (I) has formula (Ia):


5. A composition according to claim 4 wherein the repeat unit of formula(I) has formula (Ib):


6. A composition according to claim 1 wherein R¹ in each occurrence isindependently a C₁₋₂₀ alkyl.
 7. A composition according to claim 1wherein the one or more co-repeat units include a charge-transportingrepeat unit.
 8. A composition according to claim 7 wherein thecharge-transporting repeat unit has formula (VII):

wherein Ar⁸ and Ar⁹ in each occurrence are independently substituted orunsubstituted aryl or heteroaryl, g is greater than or equal to 1, R¹³is H, C₁₋₂₀ alkyl, Ar¹⁰, a branched or linear chain of Ar¹⁰ groups, or acrosslinkable unit that is bound directly to the N atom of formula(VIII) or spaced apart therefrom by a spacer group, wherein Ar¹⁰ in eachoccurrence is independently an unsubstituted or substituted aryl orheteroaryl; c and d are each independently 1, 2 or 3; and any two ofAr⁸, Ar⁹ and R¹³ directly linked to the same N atom may be linked by adirect bond or a divalent linking group.
 9. A composition according toclaim 7 wherein the charge-transporting repeat unit has formula (VIII):

wherein Ar⁸, Ar⁹ and Ar¹⁰ are in each occurrence independentlysubstituted or unsubstituted aryl or heteroaryl; z in each occurrence isindependently at least 1, optionally 1, 2 or 3, preferably 1, and Y is Nor CR¹⁴, wherein R¹⁴ is H or C₁₋₁₀ alkyl.
 10. A formulation comprising acomposition according to claim 1 and at least one solvent.
 11. Anorganic light-emitting device comprising an anode, a cathode and one ormore organic layers between the anode and cathode including alight-emitting layer wherein at least one of the one or more organiclayers comprises a polymer according to claim
 1. 12. An organiclight-emitting device wherein the organic light-emitting layer comprisesa composition according to claim
 11. 13. An organic light-emittingdevice wherein the organic layers comprise a hole-transporting layerbetween the anode and the light-emitting layer, the hole-transportinglayer comprising a polymer according to claim
 12. 14. A method offorming an organic light-emitting device according to claim 12comprising the step of forming the light-emitting layer over one of theanode and the cathode and forming the other of the anode and the cathodeover the light-emitting layer.
 15. A composition according to claim 1wherein the phosphorescent dopant has a photoluminescent spectrum with apeak in the range of 420-490 nm.